I'm using Standard Edition in this example, however, I wouldn't think it was specific to this edition. I used to boot WS2008 and Win7 from VHD as "thin" hypervisor, i.e. the VMs had full access to the hardware, this trick doesn't seem to work in Win Server 2012?

I haven't tried Win Server 2012 but I have installed windows 8 as VHD boot and run hyper-v on it no problems.

Win8/WS2012 have different boot layer - perhaps you need to use a diff BCDEdit, or perhaps you need to perform the install of the parent partition directly into a VHD using the supported method instead of messing around with BCDEdit after the fact?

Thanks for that, I had just assumed it was some form of virtualisation as it was using VHDs, I had never researched how it worked.

The plan was to have Win7 Ultimate and Windows Server 2012 Standard installed. So I build WS2012 VHD on one of my Hyper-V machines and copied it to the Win7 machine, then did what I normally do:bcdedit /copy {current} /d "Server 2012 Standard"bcdedit /set {66054000d-dd92-11dd-92a1-dc4419dac736} device vhd=[C:]\VHD\WS2012Std.vhd bcdedit /set {66054000d-dd92-11dd-92a1-dc4419dac736} osdevice vhd=[C:]\VHD\WS2012Std.vhdbcdedit /set {66054000d-dd92-11dd-92a1-dc4419dac736} detecthal onRebooted the machine, but no boot selection menu, just back into the Server. So failing that, I scrubbed the Server 2008 R2 instance and rebuilt as Server 2012 Standard, then tried the same method to boot a Win7 Ultimate VHD, again, no boot option, straight to the server. When I list the BCDEDIT, the GUIDs display as I configured them, but they are not available at boot time.

The machine has been scrubbed again for ESXi testing, but I can rebuild as Server 2012 relatively easily.